1. Field of the Invention
The present invention relates to an electron-emitting device, an electron source which uses a plurality of the electron-emitting devices, an image-forming apparatus such as a display apparatus, an exposure apparatus or the like which use the electron-emitting device and the electron source, and manufacturing methods thereof.
2. Related Background Art
There are conventionally known electron-emitting devices which are classified roughly into two kinds of electron-emitting devices: thermionic cathode and a cold cathode. The cold cathode is classified into a field emission type (hereinafter referred to as FE type), a metal/insulating layer/metal type (hereinafter referred to as MIM type) and a surface conduction type. Known as the FE type electron-emitting devices are electron-emitting devices which are disclosed by W. P. Dyke & W. W. Dolan, “Field emission,” Advance in Electron Physics, 8, 89 (1956), C. A. Spindt, “PHYSICAL Properties of thin-film field emission cathodes with molybdenum cones,” J. Appl. Phys., 47, 5248 (1976) or the like.
Known as examples of the MIM type electron-emitting device are electron-emitting devices disclosed by C. A. Mead, “Operation of Tunnel-emission Devices,” J. Apply. Phys., 32, 646 (1961) and so on.
Known as examples of the surface conduction type electron-emitting devices are electron-emitting devices disclosed by M. I. Elinson, Recio. Eng. Electron Phys., 10, 1290 (1965) and so on.
The surface conduction type electron-emitting devices utilize a phenomenon where electrons are emitted by supplying a current to a thin small area film formed on a substrate in parallel with a surface of the film. Reported as the surface conduction type electron-emitting devices are devices disclosed by Elinson, et al. described above which uses thin films of SnO2, devices which use thin films of Au [G. Dittmer: “Thin Solid Films,” 9, 317 (1972)], devices which use thin films of In2O3/SnO2 [M. Hartwell and C. G. Fonstad: “IEEE Trans. ED Conf.” 519 (1975)], devices which use thin films of carbon [Hisashi Araki, et. al.: shinku (Vacuum), Vol. 26, No. 1, p. 22 (1983)] or the like.
FIG. 11 schematically shows a configuration of the device disclosed by M. Hartwell described above as a typical example of the surface conduction type electron-emitting device. In FIG. 11, reference numeral 111 denotes a substrate. Reference numeral 114 designates an electrically conductive film which is composed of a thin film of a metal oxide formed by sputtering as an H-shaped pattern and an electron emitting region 115 is formed by an current supply treatment. In FIG. 11, a spacing L of 0.5 to 1 mm is reserved between element electrodes and W′ is set at 0.1 mm.
It is conventionally general before emitting electrons to form the electron emitting region 115 on the surface conduction type electron-emitting device by subjecting the electrically conductive film 114 to a energization treatment called “forming”. Speaking concretely, a DC voltage or pulse voltage is applied across both ends of the electrically conductive film 114 to locally break, deform or degenerate the electrically conductive film 114, thereby forming the electron emitting region 115 which is in an electrical condition of high resistance. At this stage, the electrically conductive film 114 is partially cracked and forms a gap.
The surface conductive electron-emitting device which has the gap formed as described above emits electrons from the electron emitting region 115 (vicinities of the gap) when a current is supplied to the device by applying a voltage to the electrically conductive film 114.
It is possible to compose an image-forming apparatus by forming a plurality of electron-emitting devices such as that described above on an electron source substrate and combining it with an image-forming member composed of a fluorescent material or the like.
However, the electron-emitting device disclosed by M. Hartwell described above is not always satisfactory in its stable electron-emitting characteristic and electron-emitting efficiency, whereby it is extremely difficult under to provide an image-forming apparatus which has high luminance and excellent operating stability.
Accordingly, a treatment called activation treatment may be carried out as disclosed by Japanese Patent Application Laid-Open Nos. 08-264112, 08-162015, 09-027268, 09-027272, 10-003848, 10-003847, 10-003853 and 10-003854. The activation treatment step is a step of remarkably changing a device current If and an emission current Ie.
Like the forming treatment, the activation step can be carried out by repeating application of a pulse voltage to device in an atmosphere containing an organic substance. This treatment allows a film comprising of carbon and/or carbon compounds is deposited from the organic substance existing in the atmosphere onto at least the electron emitting region to remarkably change the device current If and the emission current Ie, thereby making it possible to obtain a more favorable electron emitting characteristic.
An example of conventional manufacturing method of the electron-emitting device will be described with reference to FIGS. 19A through 19D.
First, a first electrode 2 and a second electrode 3 are disposed on a substrate 1 (FIG. 19A).
Then, an electrically conductive film 4 is disposed to connect the first and second electrodes. (FIG. 19B)
Then, the forming treatment described above is carried out. Speaking concretely, a second gap 6 is formed in a portion of the electrically conductive film 4 by flowing a current through the electrically conductive film (FIG. 19C).
Furthermore, the activation treatment described above is carried out. Speaking concretely, by supplying a voltage to the electrically conductive film, a carbon film 10 is formed on the substrate 1 within the second gap 6 and the electrically conductive film 4 in the vicinity of the gap 6. This activation treatment forms a first gap 7 which is narrower than the second gap, thereby forming an electron emitting region 5 (FIG. 19D).